A numerically controlled machine tool (CNC) executes an NC program in which various processing steps are specified one after another. For a milling machine, the relative motions between a workpiece and a tool are established and processed one after another. The milling cutter fastened to a rotating spindle removes material from the workpiece. In an NC program, besides the actual processing steps, tasks such as changing from one tool to another, starting and stopping the rotary motion of the tool spindle or feed motions are also established, that is, motions of the tool without intervention in the workpiece.
In connection with numerically controlled machine tools, it is described, for example, in U.S. Pat. No. 4,078,195, that one may make the feed of a rotating, metal removing tool a function of a parameter observed during processing, such as the input power of the tool spindle. For a constant feed, the power used for turning the spindle at the programmed setpoint rotational speed is a function of various parameters. Thus, the power is greater, the harder the processed workpiece, and the larger the processed surface of the workpiece. A tool entering more deeply into the workpiece requires greater spindle power, since at constant feed, more material has to be removed per unit of time. Thus, in order to obtain a constant high spindle power, and with that rapid processing, the feed has to be appropriately regulated.
Conventional adaptive feed rate regulations, however, are believed to have the disadvantage that, in order to use the adaptive feed rate regulation, certain commands have to be taken up into each NC program in order to control the feed rate regulation itself. These may be simple commands, such as switching on and off the feed rate regulation itself, or the establishment of certain boundary values. This means that each NC program, for which the adaptive feed rate regulation is to be used, has to be prepared for it with great effort. For NC programs for processing only a small number of pieces, this is not worthwhile.